At a recent press conference, director Robert Zemeckis, producer Steve Starkey and their A Christmas Carol stars Jim Carrey, Robin Wright Penn, Bob Hoskins and Colin Firth talked about the process and challenges of making a performance capture film. As Zemeckis mentioned, the technology has moved from medical uses to helping to evaluate one's golf swing to moviemaking.

Zemeckis said that since his love affair with performance capture began on The Polar Express he's been searching for tales that could be told in new ways with this new art form.

Following Beowulf, Zemeckis said, "I just got hit with the idea that it could be A Christmas Carol, so I went back and read the book to refresh my memory on how I might have seen it and I realized this really hadn't been realized in the way that was actually imagined by Dickens as he wrote it. This could be the perfect way we could take a classic story that everyone is familiar with and re-envision it in a new and exciting way."

"Form always follows story. So when the idea of A Christmas Carol popped in my head, there was a chance to get an actor like Jim to morph himself into all these ghosts and characters and not do it in a traditional way with a 2D camera where all these other wonderful actors would play these ghosts and things like that."

When preparing his actors for the performance-capture films, he begins with an intense table read, where initially he acts out all the roles. "When we go into the volume, as well call it, which is this block of invisible inferred light that we do the movie in, [the actors] turn it on," said Zemeckis. "And so when we're working through the scene, we're recording everything, because there's no film; it’s just harddrives running. So you're doing a performance and you're doing a scene and we do the scenes from beginning to end like you'd do a scene in theater. We work the scene out, the actors work the scene out, and what's great is we record it and when we're really going to do it, if someone says, 'Gee Bob, I'd like to walk in from the other side of the room, because I think it would feel better,' we'd say just try it. So it's like we're doing these elaborate theatrical tech rehearsals. The whole thing is like a tech rehearsal, and he hone the scene down and then all of a sudden we look at each other and say, 'Is everybody happy? Does everybody feel good about that?' And when everyone does we say okay and we move on. We break for lunch."

When performance capture first broke onto the scene, there were murmurs that actors feared for their jobs. But Starkey contradicted that notion when he said, "When you talk to actors they have just as much interest in this new art form as we do. It's freeform and it's more like acting in theater. You're not encumbered by the mechanics of filmmaking but you still get to act and play these characters that otherwise you might not be appropriate for... because of your likeness you might not be cast in that role, but in this art form you can do the performance and they can create that likeness in the computer. So you get to play someone young or someone who is taller than you are or whatever it is."

When asked about performing with the markers, Jim Carrey, who plays Scrooge and the three Christmas ghosts, said, "There are certain aspects of the technology that are so exciting and amazing creatively that you can't wait to see what it turns into. Certain aspects of the technology make things easier, to get a lot of scenes done, to do a lot of material at once. There are a lot of aspects that allow [Bob] to create the world that he wants."

"For an actor, there are extra challenges. You have to create the ambiance and the belief in your surroundings in your head," Carrey added. "You can use everything you got. The fingers turn into these long spindly looking things. It's like puppeteering in a way."

Colin Firth, who plays Scrooge's nephew Fred, was only on-set for two days. For his experience, he said when your performing the challenge is that it's "a whole run, a whole scene with no reason to stop. You're never off camera. If you stumble it's in the movie. In some ways you had to rise to the occasion of having all that freedom. There is no proscenium. There's no camera to play to. But having said all that, it's fantastic. It's even more authentic than doing theater because there is no imaginary fourth wall. Or even if you're doing theater in the round, you have to worry about the people in the gallery. Or you have to worry about the marking or blocking. You can do exactly what you want at any time."

Robin Wright Penn, who plays two roles in the film, is a vet of performance capture, having worked on Beowulf. As for the advancement of the technology, she marked, "Even more so with this one, our eyes, every movement and the minutia of the acting that we all did, you see on the screen. And yet, we could change the size of the eyes with the animation. I said at one point, what if I could look like one of those Whoville girls with those big ole blue eyes. And [Robert] said, 'We can do that.' Your every movement is captured and it's fascinating to watch. It really comes through. It's so moving."

As for the stereoscopic 3-D elements, she commented, "It's like watching a 2D performance, but you feel like you can reach out and grab Jim's hand and feel the snow falling at the same time. You're actually in the environment. That's what's so incredible about it."

Bob Hoskins, who plays Scrooge's former employer Fezziwig, worked with Zemeckis on the revolutionary Who Framed Roger Rabbit? Commenting on the difference between that film and this one, he said, "Before everything had to be dressed and we shot the film and then they blew up the frames and painted on the characters. With this they shot all the performances and then they paint the background, put on the costumes, and do everything. So it was the complete reverse. And what was extraordinary was the fact that once you're covered in all this stuff you got nothing else to do but to concentrate on your performance. They've taken all responsibility from you. It's extraordinary."

Carrey added, "There were times when as film actors, you're use to having the proscenium in your head somewhere and there are boundaries, but in this there are no boundaries anymore. It's odd not to have any boundaries. Once in awhile, I'd say to Bob, 'Can you just stick a camera there? Just so I can feel someone, because I'm use to having someone.'"

On that Zemeckis said, "I learned this early on. I put a marker on the camera and then it becomes a character, and immediately I'm creating shots in the virtual world, but what it also does for the performances [is that] the camera [becomes] a dance partner. The camera is another performer, so the camera creates rhythm, so the actor feels the camera moving from here to here so he knows when to deliver the line. So that is a very helpful tool because we've all been trained in having that camera as a partner."

Rick DeMott is the director of content for Animation World Network, VFXWorld and AWNtv. Additionally, he's the creator of the movie review site, Rick's Flicks Picks, which was recently named one of the 100 best movie blogs by The Daily Reviewer. He has written for TV series, such as Discovery Kids' Growing Up Creepie and Cartoon Network's Pet Alien, the animation history book Animation Art, and the humor, absurdist and surrealist website Unloosen. Previously, he held various production and management positions in the entertainment industry.